1. Field of the Invention
The present invention generally relates to headphones and, more particularly, is directed to a headphone which can be closely fitted into a cavum concha of a listener's ear to prevent sound from escaping to the outside to thereby improve acoustic characteristics thereof.
2. Description of the Prior Art
A headphone of a so-called vertical-in-the ear type has hitherto been proposed, in which a housing portion having a sound radiating unit is inserted into a cavum concha in an auricle of a listener's ear by making effective use of a resiliency of a headband and held therein by a pressing force. As is described in U.S. Pat. No. 4,668,842, this type of headphone includes a housing portion in which an electroacoustic transducer element and a diaphragm are incorporated and a protector member having a large number of sound radiating apertures on the sound radiation surface side of the housing portion.
The above conventional headphone includes the housing portion whose outer shape is matched with those of the electroacoustic transducer element and the diaphragm. Therefore, the shape of the housing portion becomes a flat cylinder. When the housing portion of the above shape is fitted into the cavum concha in the auricle of the listener's ear, the housing portion cannot be closely fitted into the cavum concha appropriately along the shape of cavum concha. When the housing portion of the headphone is fitted into the cavum concha, the listener unavoidably feels physical discomfort. In particular, when the housing portion is fitted into the cavum concha, a part of the housing presses a tragus in the auricle of the listener's ear. There is then the disadvantage that, when the listener wears the headphone for a long period of time, the listener feels pain too strong to permit use of the headphone.
Further, since the housing portion is not closely and appropriately fitted into the cavum concha, sound from the sound radiating portion escapes to the outside of the auricle from a spacing between the cavum concha and the housing portion. As a consequence, acoustic efficiency of the low frequency component is lowered and the escape of the high frequency component is increased, thereby deteriorating the acoustic characteristics of the headphone.